Telephone system



Nov. 3, 1931.

TELEPHONE SYSTEM Filed Nov. 25, 1929 4 Sheets-Sheet l ,\\\1ww\\ MQ Q 1mm f a u Q y W wm MM: $4 ufv lx M i. FHL i# N h NQ i iln. m1 m... mwowm n.. J V EQ w QQ Nm @N1 ,x M M @ha i; N ,F q, 1 wl .Wlilml q N2 a www@ n f wv u Q |||||||||.|l| uw@ RH QQ .1 www n i QQ S Q` QCM* i n Q n MII RR S W @l H x a l 'IIN v n Q I.- GQ r wm..

, InuEnm-s Nul-'man H. Saunders Clarence E 'Lm-max m Nov. 3, 1931. N. H. sAuNDERs ET AL 1,830,678

TELEPHONE SYSTEM Filed Nov. 25, 1929 4 sheets-sheet 2 Nul-"man ,Clarence E. lst-.ax

MAM

N0V- 3, 1931- N. H. sAUNDERs ET AL 1,330,678

TELEPHONE SYSTEM Filed Nov. 25, 1929 4 Sheets-Sheet 5 34 PHP 542 i hEELEASE 5/6.

T0 CHARGE? Norman H. Saunders Clarence E. Lun-Lax NOV- 3, 1931. N. H. sAUNDERs ET AL 1,830,678

TELEPHONE SYSTEM Filed Nov. 25.4 1929 4 Sheets-Sheet 4 j W m l I Rw THMES Il'llllll NNWIIIIIIIIIIIII I l l lllll llll llllllll v mw WY i Ivars-mrs Norman H. Saunders Patented Nov. 3, 1931 f ST cuirs NORMAN H. SAUNDERS, OF HOMEWOODLND CLARENCEy E. LOMAX, OF OAK IFA-RK,y 'L'LLINOIS, ASSIGNORS TO' RESERVE HOLDING COMPANY, OF CHICAGO, ILLINOIVSyA CORPORATION or DELAWARE TELEPHONE SYSTEM Application mea Nvmber 25, 1929. serial 110.409,451.

The present invention' relates tothe telephone system 'fort giving servicel to rather thinly populated rural districts; and the main object is vthe provision of an eilicient and economical automatic switchboard of the so-called lineswitch-connecting type for giving party-line service to rural lines.

Lineswitch-connecting switchboards, it may be explained, are used in small systems of not more. than one hundred lines. In such a switchboard, a single connector is associated with all of the local trunk lines and is, therefore, taken into use when any trunk line is seized and it is operated to malte con` nection with a desired line and to signal the called subscriber on the line, after which'the lineswitch on the called line is operated to connect the called line with the same localv trunk with which the callingline is connected, and the local trunk is disconnected from lthe connector, leaving the connector free for user in connection with fthe other local trunks. The lineswitclrconnecting systems heretofore known have been developed'for the most part fork use in connection with private automatic exchanges, andyfor that reason are not particularly suitable for use in connection with public exchange systems. It is, therefore, an object of the invention vto revise the lineswitch-connecting switchboard and render it suitable forfuse in small public exchanges, called community Vautomatic exchanges.

One object of the. invention is to provide means for signalling the desired one of a plurality of subscribers'on a party line. y f

Another objectv is to Vprovide means for giving the calling vsubscriber a distinctive tone in case he ycalls an unassigned number and thereby causes the connector to connect with vacant linefterminals.

Another object is to provide a connector suitable for use in a lineswitch-connecting system wherein-the lines are of the so-called local-battery, simplex-dialling type.

t is a further object to make such Vchanges and alterations in the connector, consistent with efficiency and economy, asl willfollow lines.

from the altered character of the subscribers A further object is the production of new and -improved line equipment which will lessen the-number of trunks taken up by defective, partially-grounded lines. This is particularly advantageous in certaintimes of the year when storms or other natural agents do much damage to long open-'wire lines. i f

It is a further object to put the improved line equipment into the circuit of a plunger lineswitch such as is yused in the lineswitch- Vconnecting switchboard and to so arrange the lineswitch that it does notoperate responsive to the removal of the receiver (and consequent grounding of the line) until ringing current is projected over the line by the turning o f the usual hand generator.

Thel various objects and features of the invention will be better understood upon a furtherperusal of the specification in connection withV the Y accompanying `drawings comprising Figs. 1 to 4.

The-drawings show by means of the usual circuit dia grams a suiiicient amount of equipment in a community automatic exchange em` bodying the features of the invention to enable the invention to be understood. `V

Geaeradescription Fig. vlshows three lines incoming to aline` switch-connecting, switchboard. The line SL is a subscribersparty line; the line. 'ILl isa trunllzv line connecting the community `automatic exchange with a distant `manual ex'- change, and the. trunk l-ine TLQ isa second trunk line between the two exchanges At the automatic switchboard, thejthree lines above mentioned terminate in the lineswitches LS1, LS2, and LSE, respectively.

These lineswitches are of the usual plunger type, mechanically, and they, together with c the other lineswitches of the switchboar d,vare

controlled by the master switch MS, Fig. 3. i This master switch is of the usual type, me-

chanically, and it has its circuits suitably revised to enable it to operate in the desired The lineswitches, of'which three are shown in Fig. 1, have common access to ten local trunks, of which the local trunk LT10 is shown in Fig. 1. Each of these local trunks is normally connected with the connector C et Fig. 2 with the result that a seizure of any trunk results in the seizure of the connector.y Mechanically, the connector C is a two motion switch of the usual step-by-step type having its bank contacts arranged in lten horizontal rows or levels. Auxiliary to the connector C, there is a code selector CS, arranged tu respond to a single digit, for which reason it has a rotary motion only.

The apparatus shown in Fig. 4 isauxiliary to the connector of Fig. 2 and includes a ring'V ing interrupterRI Vthe dial-tone buzzer DT the several relays shown along the bottom of' the sheet; and the auxiliary switch AS. The switch'AS is a switch having a continuous rotary motion and it has sixteen positions.

rthe position in whichthe switch normally stands is called position 1. The positions in which the various cam springs such as 403, 404.' etc. engage their cooperating contacts are indicated adjacent to the cams. For example, cam 403 engages its Contact continuously in positions 2 to 16, while cam 404 engages its associated contact in position 1 only.

The equipment shown below the dotted line in Fig. 3 is power and supervisory equipment, collectively designated as power eauipment and given the reference character PE.

General description of operation The general operation ot thesystein will now be outlined briefiy.v `When a call is made, for example over thesubstation S1 lon the party lineSL, the receivenisremoved,

grounding the line through the two windings cf the ringer R, butno current lowsover the line because of the circuitV connectionsat the lineswitch LS1; `The hand generator HG is' next operated and causes the lineswitch LS1 to operate in a manner jtol be described 1riereinai'ter and to lock itselfover the subscribers line. By operation of the lineswitch LS1, the local trunk LT10 is seized.l because the master switch shown in Figj is standing on the tenth local trunk atthisvtirne.`V The trunk LT10 is connected to the connector C of Fig; 2. through contacts of thetrunk relay 124, with the resultv that the connector C is taken intol use. When this happens, the ,auxiliary switch AS startsto operate under lthe controlof theinterrupter comprising relays 412 and 413. so as to release the connecf tor at theend of predeterminedtime in case thedialling is not completed.

The'subscriber dials the two digits assigned to the desired line, causing the connector C to vbe operated vertically and then in a rotary movement, after which the subscriber dialsy the c ode digit assigned to the desired station. causing the code selector CS to be operated.

As soon as the code selector has been opgtion, of the auxiliary switch AS Fig. 4 brings about'the above operation.

lFollowing the connection of the two lines together byway of the local trunk LTlO, the

inaStersWitch MS operates (having beenk Vmaintained in the same positionwhilethe call was being putthrough) topreselect another of the local trunks. The remaining line switches are prevented from operating responsive to control'y over their respective lines until the initiated call has been put through anda new trunk has beenpreselected.

Detailed description; call from substation' S1 to the manual exchange vThe system having ybeen explainedl generally, a detailed explanation will now be given. For this purpose it willbeassumed that the subscriber at substation S1 desires toconverse with a subscriber who mustbe reachedby way of the manual exchange, to which connections are extendedl over one of the trunk lines TL1 and TLQ. 4 The connector 'number of the'manual exchange-is O1, and the digit 1 kis added to this number'in order to operatethe code switch to signal the opertor. Accordingly, the completenumber is When the receiver is removed at substation S1, a talking bridge is placed across the conductors of the line at contact 8; the transV mitt'er T is Vconnected in the local-battery cir-v cuit with the primary winding of the inductioncoil 102 at contact 9; and at the contact 7 a ground connection is made to the two conductors of the line through the contacts 105,

of the calling device CDv and the `coils of the ringerR. Nothing happens for the time being as the result ot'I thisground Aconnection on'account of the fact thatl the line is devoid does not re- 'l ing line to of the subscribers line through the contacts of the bridgeeut-ottl arm 108, operates in' response to the ringing current. Upon oper ating, relay 106 rst closes its Contact marked X, thereby closing a locking circuit 'for relay 106 over the two conductors ofthe line in parl,l

allel, to groundthrough the switch-hook con# tact 7. Upon operating further, relay 106 short-circuits its upper winding so as to ren- `f der the relay slow-releasing.

As a further result of its operation,l relay 106 closes a circuit from the grounded, chain conductor 133 for the lower Winding (the pull-down winding) of the lineswitch mag- 110-#113 ot the lineswitch, extending the connection through to the preselected local trunk LT10. The conductors of the subscribers line are now extended by way of the talking conductors 121 and 123 of the local trunk LT10 and the common conductors 127 and 131 to the connector C, Fig. 2.

Line relay 202 of the connector C now oper-V ates through the two windings on the impedance coil 201 in parallel, and over the callground at the switch-hook contact 7 j v Upon operating, line relay 202 closes al circuit for release relay203 through the series relayv 211. Relay 211 does not operate at this time owing tothe fact that itis shunted by the rotary magnet 21'?, which is connected in parallel with it-through the middle lower armature, normal, of relay 204C and armature 224,normal. Magnet 2,171 does not operate owing to the relatively hi'ghresistance of releaserelay 203.k v f Upon operating, relay 203 disconnects the test conductor 128 of the master switch MS, Fig. 3, from the start conductor 12,9 and connects it to-ground, at armature 213, thereby closing a circuit over conductor 128 and through wiper 315 and over conductors 134 rand `122 for the combined holding and cutotl winding (the upper winding) of magnet 107 of the lineswitch LS1.'V This 'circuit in` cludes the spring 111 of the lineswitch and its associated Contact. The currentf10w through this winding is suilicient to maintain the bridge-'cut-oi armature 108 and the plunger arm 109 operated after 4relay 106 falls baclr and opens the circuit ot" the pulldown winding ot' the magnet, as it very shortly does.

As a further result of the operation of release relay 20.3 of the connector, the openchain. conductor 13,0: isy grounded. at armature 214k,l operating the slow-acting open.-

chain relay 313 of the` master lswitch and thereby removing ground potential from chainf` conductor 133. The removal of ground from conductor 1.33 opens the circuit; ofthe4 lower Winding of magnet 109 at this time' whether the line 106 has fallen back or Y not, and it prevents the operation of further lineswitches.

As a further result of its operation, 4relay 203v Icloses a locking circuit for itself at its inner lowerarn'iature, thereby preparing the Aoperating circuit t'orthe magnets as will hereinafter appear, and at its upper armature closes a circuit through the o-normal contacts 215 for relay 204. Relay 2011 operates and at itsmiddle lower armature disconnects therotary magnet 217 from in parallel with relay 211 and substitutes the vertical magnet 216. The 'circuits are now in readinessv for the calling subscriber to start dialling'.` As a 'further result-of its energization, relay 203, at' its lower armature, grounds'the tone-start conductorl 256 through thenormally closed contacts controlled by armature 225 of switching relay 212, closing a circuit 'through cam Lllllof the auxiliary Switch AS lies the calling subscrlberthat he may new dial the desired number. l f

`its a further result of the operation of relay Lle, a point in the restoring circuit of the auxiliary switch AS is opened at the upper armature of the relay and a ground potential is extended over conductor 431 to the interrupter comprising relays 112 and L113. Relay v413 operates, through the associated resista-nce andi removes the short circuit lirom around relay i12, at the same time closing a circ uitA tor the said relay l-l2. When relay 412 operatesit short-circuits relay 41"; Relay 113 falls back after a slight interval and opens the ci-i'cuitot relay 11-12 and replaces the short circuit aroundA its winding. lllllien relay i12 falls back, relayfl13 reoperates, this operationicontinuing as long` as. conductor 1131 remains grounded. The copper collars placed on the upperends lof the relays L112 and 413 render the relays slightly slow to operate, having a steadying etec upon the operation. l

rllhe audible sound produced in. the receiver at the calling telephone notiics izo

Each .time relay 4112 operates, it closes a circuit for the operatingv magnet 101 ofthe auxiliary switch' AS."` Each time relay V412 412 and 413 is adjusted to operate lat a Vrate l'so which will allow suicient time for the .dialling of a complete number .before the auX- ili'ary switch AS completes itscycle and returns to position 1.

l/Vhen the switch AS leavesposition 1, contact 404 opens the initial circuitof relay 416,

but relay 416 remains operated in a locking circuit from the grounded conductor 256 in series with relay 415. Relay 415, having been shortcircuitedheretofore, now operates in series with relay 416 and` prepares a cutoli1 circuit to be subsequently described;

As a further result of the placing of ground potential on conductor 256, the differentially wound tone relay 414 operates in a buzzerlike manner, and sends a tone current directly over the vacant-tone conductor 255, and an interrupted tone through contacts of relay 1-12 to the busy-tone conductor 251. In connection with the operation of relay 414, it may be pointed out the upper and lower windings are reversed withthe respect to one another and that, upon operating, the relay lconnects the lower winding in parallel with the upper winding, causing a neutralization of etfect and a consequent retraction of the armature of the relay. This operation continues at a rather rapid rate and gives rise to-a. characteristic tone current.

Inv case the calling subscriber does not dial the number and thereby cause the connector to remove ground potential'from the tonestart conductor 256, aV cut-ofi1 circuit is completed fromv grounded conductor 256, and through cam 404 and the lower armature, operated, of relay 414, to conductor 254, when the auxiliary switch ,AS again reaches position 1. Over this cut-oli;1 circuit. relay 124 of the local trunk LT10 is operated to cut oit the connector and return it to normal use in a manner to be subsequently'pointed'out.

It will now be assumed that the calling subscriber, upon hearing the dial-tone transl mitted back to his substation over conduct-or 131 ofthe connector and over the lower vtalking conductor of his line, as above pointed out, dials the three digits 0, 1, and 1 without undue delay. Y f

When the first digit 0 is dialled, the circuit of line relayy 202 of the connector C, Fig. 2, is opened ten times at the contacts 105 of the calling device CD, uponthe return of the calling device to normal. It will be noted that the oli-normal springs 6 exclude the coils of the ringer R from the dialling circuitfas 'long as the dial is off-normal.

Each time its circuit is opened, line relay i 202 falls back and places a shunt around the winding of release relay 203, thereby closing a circuit for the vertical magnet 216 throughvv the grounded inner lowerv armature of the operated relay'203, contacts of line relay 202,

and the'middle lower armature, operated, of

relayi204. Vertical-magnet 216 operates each timethis circuit is closed by the shunting of release relay 203,v and lthe magnet restores each time the shunt is removed from around? relay 203. Each time relay 203 is shunted, a direct circuit. is closed for series relay 211 in parallel with vertical magnet 216. Relay 211 operates, and it is so designed and pron portioned that it remains operated through- 216, the wipers A to E of the connector are raised step by step until they arrive opposite the tenthlevel of bank contacts. When relay 211 operates, it closes a locking circuit at its inner lower armature for relay 204 through e the inner contacts of thesaid relay. This circuit is effective to maintain relay 204 operated after its initial circuit is opened at oli'- normal contacts 215 upon the lirstk vertical step ot the switch.

Vhen relay 211 falls back at the end of the vertical movement, it opens the locking circuit o'lf relay 204 at its inner lower armature. Relay204 fallsback and transfers the operating circuit from the vertical magnet 216 to the rotary magnet 2717 at its middle lower armature. A

When the switch is operated to thetenth level (as it now is) the 0-level contacts 218 close, completing a circuit for,l the 0a-level relay 209. Relay 209 operates in preparation for a trunk-hunting operation on the tenth leve l. Y v e f n When the secondl digit 1 is dialled, the single momentary deenergization of the'line relay` 202 results 'in the delivering of an impulse `to the rotary magnet 217, and in the delivering'of an impulse to the series'relay 211. Series relay 1211 again energizes, and rotary magnet 21'? `operates to rotate the wipersA to E onto the first setof bank contacts O1 in the f enth level. This set of bank contacts-is shown inthe upper right-hand portion of the drawing.` Relay 211 disconnects the test wiper C from'the lower .winding of switching relay 212 and connects it' instead to thevwinding ofbusy relay 210 so as to enable the busy relay 'to operate over wiper C' in case thecalled line tests busy. Relay 211 also shunts the contacts 'of relays 208 and 210 at its lower armature so as to prevent a premature opening of the operating circuit in case either relay 208 orl relay 210 should operateduring the rotary movenient. n

Assuming that the trunk line T L1 'of Fig.

-1 is busy, there is a ground potential onthe 0` lead thereof, and, as a result, busy relay l210 operates assoon as `the C wiper of the connector lands upon the c contact of set O1. As soon as the rotary magnet 217 deener- `gizes following this rotary step, relay 208 energizes from ground potential on the c conductor through the connection between contacts c and al of set O1, the D wiper ofthe connector, inner lower armature and working contact of relay 209, and the interrupter contacts of rotary magnet 217. Upon operating, relay S closes a locking circuit for itself at its innerupper contacts throughthe inner upper contacts ofrelay ,209 and the interrupter contacts of rotary magnet 217. At its middle upper armature, relay 208closes a circuit for rotary magnet 217, through the upper contacts of relay 209. Rotary magnet of the connector, butl relay 208 does not opg 217 reoperates and advances the wipers A to E of the connector into engagement with the bank-contact set G2, the second contact set in the tenth level. l1`he bank-contact set O2 is the set associated with the trunk line TL2,

i. i Y' The furtherk operation depends upon i Whether the trunk line T112 is busy or idle. In case this trunk line alsojis busy, the busy relay 210 remains energized over .the Ciwiper erate again owing to the fact that the c and d contacts of set G2 are not connected together. Accordingly, the wipers yof the connector remain on the bank Contact set O2 in spite of ceases,fit closes a locking circuit for busy rethe busy vcondition of the trunk line TL2.

r When the slow-acting series relay 211 falls back, as it does when the rotary movement lay v.210 from ground by way of the upper armature of release relay 203, through the innerupper armature, operated of relay 210,

and the normally-closed contacts controlled by the upper armature of relay 211. l/Vith yrelay 211 restored and relay 210 operated, the

locking circuit of release relay 203is opened and no further impulses can be delivered to;v the rotary magnet by subsequentdeenergizations of the line relay when the next and last digit is di'alled. The interrupted tone from:

the busy-tone lead 251 is connected through.; the lower armature of relay 210 and the low'- er armature of relay 212, andthrough the' condenser 271 to the lower talking conductor 131 to notify the calling subscriber `of the busy condition.

lf the calling subscriber replaces his receiver immediately upon hearing the busy.y tone, the connector releases responsive toV the falling back of the line relay when its circuitis opened Vat the. substation. If he does not hang-up immediately, the connector releases responsive to the operation of cut-oft relay 124 responsive to auxiliary switch AS reach- 1 ing position 1 after having been advanced through its other positions. ,Y

Assuming now that one of the trunk lines is found to be idle, the trunk line TLl forl example, a connection is made to the trunk line by the energization of switching relay 212: Since-the line is idle, busy relay 210 is not energized 4when the wipers come -to rest,

and a circuit is completed for the `lower winding ofV relay 212 upon thefallmgback. of series relay 211. This kcircuit is from ground through the upper contacts of the release relay 203, the inner upper armature, normal, ofl busy relay 210, upper contacts of relay 208, lowerwinding ofy relay 212, upper armature of relay 211, and the inner upper armature of relay 212 to wiper C. rlhis circuit is completed to battery overthec contact l and c lead of vthe Contact set O1 and over the means of its lower winding landzcloses a locking circuit for its upper windingiat armature 221; at its inner vupper armature it replaces the connection to the C wiperthrough thc lower Vwinding of the relay with adirect ground connection; at armature 2241it discon- .nects the operatingV conductor from rotary magnet *217 and extends it to the operating magnet 229 of the code selector CS.

When the calling subscriber ldialsy the vnext digit'l, one impulse of current is delivered to the operating magnet 229 of the code selector CS, andthe wipers 227 and 228 are advanced onto the first set of bank contacts.

Series relay 211 is reoperated as before, and,

when it falls back at the end of the digit, it

closes acircuit for operating busy relay 210 `at its inner lower armature through the olfnormal cont-.acts 226 of the code selector CS.

`Vlhen relay 210k operates with switchingre lay 212 operated, the ground potential is disconnected at armature 219 from the tonestart conductor256 and is transferred tothe interrupter-start conductor 252. Upon the removal of the vground potential from con- .ductor 256, relays 415A and 416 fallback; tone zrelay 414 ceases operating; and .the inter- :rupter comprising relays :412 and 413 stops operating. 1n addition, a, circuit is 4closed through contacts of relays 417 and 416, and

`through cam 403V (closed in positions 2 to 16), and the interrupter contacts 402 of stepping magnet 401, for stepping relay 411 of the auxiliary switch AS.' Relay 411operates and closes a circuit for magnet 401, whereupon magnet 401 operates and opens the circuit ofthe stepping relay. The stepping relayfalls back and opens the circuit of the operating magnet, whereupon the operating magnet falls back and again connects up the V'steppingV relay.

vuntil the stepping-relay circuit is opened at This operation lcontinues carn`f403 when the auxiliary `switch leaves position 16 and goes into position 1;

' 41/Vhen the auxiliary switch reaches position 1, a circuit is closed from the grounded 'interrupter-start conductor 252 for the in- `terrupter-'start relay 417 through cam 405 (closed in position 1). Relay 417 operates AVand locks itself to conductor 252 at its upper "armature, and at its inner armatureit opens "a further point in the restoring circuit of the Aauxiliary switch and starts the interrupter comprising relays 412 and 413 to operating again. l

At armature 424 a circuit is prepared for "the ringing-control relays 418-422, and at armature 423 the operating circuit of the ringinginterrupter RI is closed. The ringing-interrupter magnet 410 is differentially wound, and the interrupter accordingly Yoperates in a vibratory manner, as it connects vsecondary winding and is delivered to the up its second winding in opposition tot-he iirst each time the vibratory springl 411 .thereof is attracted. The lower contacts of the pendulum 411 control the current-supply to the primary winding `of the associated .y transformer, with the result that an alternatinff rinfrin current is reduced in the "connector over conductor 257 lihen the auxiliary switch AS reaches position 2', a circuit is closed through arma-Y ture 424 and cam 406 for relay 418, through c contacts of relay 419. Relay 418 operates and I locks itself in series with relay 419 through' contacts of relay 421. VRelay 419 does not operate for the time being owing to the factk that it is short-circuited `by the initial circuit of relay 418. Relay 418 also places` a ground potential at its upper contacts, and through contacts of relay 420, on the revers- "ing conductor 253, preparatory to operating the reversing relay 206 of the connector.-

` ground potential also extends through contacts of relay 419 to the pick-up conductor v`259, operating pick-up relay 205 off theeonlnector through armature 222 of relay 212,

and the middle upper armature of relay 210.

Pick-,up relay 205 locks itself at its upper' armature through contacts of the restored' `relay 204 and contacts of the operated relay 203. Relay 205 also connects up thereversing relay 206 to the grounded reversing" conductor 253 atits inner armature, whereupon the reversing relayoperates and con- I nects the Vringing relayy 207 to the upper yen `wiper 227 of the code switch CS through the lower contacts of the pick-up relay 205. The Y reversing relay is provided for the purpose yof shifting the connection back to wiper 228 has been sent out, so as to permit the second' of the code switchCS after one code digit code digit to be sent out under the control r11, 13, and 15.

y:il,tarima of wiper`228 in case the setting of the code switch is in 'accordance with a code-selecting :digit to which two code digits are assigned.

- As soon asthe auxiliary switch AS leaves position 2', the initial circuit of relay 418 is opened whereupon relay 41.9 operates in series with relay 418, and `removes ground from the pick-up conductor 259.

t will be noted` that conductor 260 is grounded by cam 409 in positions 7 and 11;

that conductor 261 is grounded by cam 408 in `of ringing current to be made to the trunk line TL1 from thegenerator lead 257, through the inner armature of the ringing relay 207, and over the A wiper, to the a lead of the trunk line TL1, a 'return circuit being pronok videdover thee lead of trunk line TL1, and

throughthe E wiper of the connectorto ground at the lower armature ofirelay207.

Then the switch AS reaches position 9, a

circuit is closed at cam 406 through the lower armature of the operated relay 419 for relay 420, and this circuit remains closed until the auxiliary switch passes through position 15.

Relay 420 new operates andv locks itself through relay 421, which relay is short-circuited for the time being, and at its upper armature relay 420 removes ground potential froni the reversing conductor 253, whereupon reversing relay 206 falls back and shifts ringing relay 207 from in connection with wiper 227 into connection with wiper 228. Accordingly, the application of ringing current to the line (if any) after the auxiliary switch has reached position 9 is under the control of Vwiper 228 of the code switch.v In this case, -sincewiper 228 is standing lonthe iirst contact in4 its bank, which Contact is not connected to any of the conductors 250-252, there is no second application of ringing current to the trunlr line TL1. It will be understoodof course, that when the code-selecting digit is anything above 3, a second code ringing digitl is sent :during the passage of .the auxiliaryswitch AS through positions .1l-.15.

It will be noted that the distant end of the trunk line TL1 terminates in the jack J 1, with ywhichis associated the drop D1. The drop D1 responds to the ringing current and displays the usual signal to the operator to attract her attention to the call. If the operator responds immediately by inserting the plug lof a cord circuit (not shown) a circuit is 'completed from ground, through the cord circuit, over'tlie two sides of the line Til in i' parallel, and over the a and e leads of the line to the contact set O1, Fig. 2, and thence to battery through the A and E wipers of tlie connector by way ot the back contacts of the armatures of relay 207 .and the combined change-over and ring-cut-oii' relay 204. In

` this case, relay 204 reoperates, and at this y ing contact of the upper armature is ground-k time places ground potential on conductor 126 at its upper armature, because the worked through contacts of the operated relays 203 and 212. The placing of groundpotential on conductor 126 results in an operation to be described subsequently.

In the present case it will be assumed that the operator does not respond immediately and that the relay 204 is not operated as above described. In this case, the operation ofthe auxiliary switch AS continues, following the application of ringing current in position 7, and the opening of the circuit of reversing relay 206 by tlie operation ot relay 420 in position 9, until position 15 is reached, whereupon the initial circuit ot relay 420 is opened at cani 400. When this occurs, relay 421 operates in series with relay 420 through the lower contacts of the latter relay, and through contacts of relay 422. Upon operating, relay 421 opens tliecircuit of relays 418 and 419 attlie resting contact of its armature, and it closes a circuit for relay 422 through the asso- 'u ciated resista-nce, at the same time removing the normal shunt from around the winding of relay 422. Relay 422 operates and opens the circuit of relay 421, whereupon relays 420 and 421 fallback, and relay 421 opens the circuit of relay 422, at the saine time replacing thesliunt around the winding of relay 422 so asto render the relayslow in releasing.

Relay 422, shortly falls back and again closes ductor 135, and the normally-closed contacts n controlled by the upper armature of relay ist,

to relay124. Relay 124 thereupon operates and locks itseli1 to ground over the line .Y relay 203, at its upperarniature, opens the-*12o of the calling subscriber and conductor 121, at the same time opening the initial circuit over conductor 135` and, in addition, discoiinecting conductor 121 from the corresponding conductor 127 extending to the connector C. rt its lower armature, relay 124 disconnects conductor 123 from the corresponding conductor 131 extending to the connector, and connects it to the impedance coil 125. At its inner upper armature, relay 124 places a ground potential on release trunk conductor 122 so as to provide `a holding circuitor/the established connection after `the ground potential is removed from the branch conductor 134, `as it will be shortly.

down circuit is closed 'for the lower Winding v of the inagnetof lineswitoh LS2 byway of the upper contacts of relays 210 and 212 of the connector, and over the B wiper and cor- 7275 responding contacts in set O1, and the b lead ofthe lineswitch LS2. When thisxcircuit is closed, the lineswitch`LS2 operatesand connects the trunk line T121 with the local trunk LTlO. The upper winding of the 'lineswitch A80 Y magnet now receives currentV from the grounded release trunk conductor 122 so .as to maintain the lineswitch operated and the line relay thereof' disconnected after the ycircuit for the lower winding lias been openedf v Vlhen the relay 422 falls back responsive to the deeiiergization of relay 421, it opens the initial circuit of the pull-down Vwinding of the magnet of lineswitcli LS2, leaving the .4s ing the plug (not shown) ofa cord circuit `into' the jack J 1, she mayconverse with the subscriber at substation S1 and complete thooi connection tothe desired line.

' lll'lienconductors 121 and 123 are disconnected from conductors 127 and 131,.by relay 124, Fig; 2, line relay 202 falls back andshort circuits release relay 203, at the same time' 100 open-circuiting the relay. The operating magnet 229, to which the operating circuit has been extended, is not operated now because ground potential has been removed from the lower armature of release relay 2O3-io5 at the inner lower armature of busy relay 210.

After an interval, release relay l203 falls back, and at its lower armature removes ground potential from the interrupter-start conductor 252, whereupon' 'the interrupterilo start relay 417, Fig. 4,. falls back andl stops the operation of the associated interrupting apparatus, and vcloses the 4previously-discussed restoring circuit for the auxiliary 'switch through. the upper contacts of relayslii 416 and 417 and the cam 403, closed in positions 2te 16. As a result, the auxiliary switch is restored'iinmediately to position 1. i

As a further result of its deenergization,

Vspo'nsive to the opening of its circuitat the` 125 lower armature of relay 203. f j

At its lower armature, rela.'T 203 closes a circuit througlioi-norinal c0ntacts'232 for the `release magnet 231 of the connector, and itl closes a parallel circuit through armature 130 As a further result of the application olif-'I0 ground potential to conductor 126, a pulllineswitch held operated'by the upper wind-Zito soon as theoperatorresponds by insert- 4220 of relay 210 for release magnet `230 of the code switch CS. When the code switch CS'reaches its normal position responsive to the energization of release magnet 230, relay 210 fallsback because its circuit is opened at oli-normal contacts 226, and it opens the circuit of release magnet 230 at armature 220.

Vhen the connector C is restored to normal position by the action of release vmagnet 231,

conductor 129. Start relay 312 of the master switch MS now energizes over conductor 134 (grounded at contacts of relay 124) through the tenth contact in its bank and wiper 315,

,conductor 128, armature 213, normal, and

conductor 129. Upon operating, start relay 3,13 at its inner armature` closes a holding circuit for the open-chain relay 313n from ground through the low-resistance righthand VwindingV of supervisory relay 317 -be fore the said open-chainrelay has 'had time -to fallback; and, at Vits lower armature, re-

lay 312V extends the ground potential from #the right-hand winding of supervisory relay 317 to the locking magnet 311. llagnet 311 operates and unlocks the associated locking segment, allowing the spring 304 to drive the master switch MS in a counter-clockwise start relay 312 remains Operated until an idle ,V

i ve5 direction and line up the plungers (not shown) of the unoperated lineswitches opposite an idle trunk. A ground potential is encountered by wiper 315 on each bank contact corresponding to a busy trunk, so that trunk isreached, whereupon the start relay falls back and opens the circuit of the openchain `relay 313 and the circuit of magnet 311. The locking magnet 311 thereupon falls back and again locks the locking segment of the master switch. Relay 313 now falls back;-

ground potential is restored to the chain conductor 133; and the apparatus is in readiness to receive and dispose of another call.

During conversation, holding current flows over the calling line SL and over the trunk line T111, inV parallel, so that relay 124 is maintained energized until the plug (not shown) ot' the cordcircuit is removed Jfrom the jack .12ct the trunk line, and until the receiver is replaced at substation S1. When this occurs, the current flow through relay 124 and the impedance coil 125 ceases, and relay 124 falls back, again. connecting conductors 121 and 123 with the common conductors 127 and 131, and removing ground from release-trunk Vation of the master switch MS, Fig. 3.

conductor 122. This'latter operation' opens' the holding circuit of the upper windings of the magnets of the lineswitches LS1 and LS2, whereupon both line switches restore to the position shown in the drawings.

- `From the foregoing explanation, itl is thought that it will be understood how any desired connection may be set up, such as for example from one local line to another local line, or from the operators switchboard over one of the trunk lines to a local line. It may be pointedout that when a local line is called the fO-level contacts 218 are not operated, and that the switch-over relay 209 is, therefore, not operated to give the connector an automatic hunting movement. Accordingly,

when a local line is busy, the busy tone is returned by the action of relay 210, and there isno further advance of the connector wipers,

asis the case when the operator is calledy and the trunk line TL1 isbusy, as hereinbefore described.

@all 250 vacant Zine terminals 2 (with which the wipers of the connector are brought into engagement when thev irst two digits of a number are 9 and 2),`1s not connected to a subscribers line. Accordingly, thc CZ contact in this terminal set is connected. to ground, ,as shown, so that relay 208 operates over wiper D of the connector and through contacts of relay 209 when the wipers land on contact setr 92. At its lower armature, relay 208 breaks the connection with dial-tone conductor 258 and connectsup the vacant-tone conductor 2,55. The continuous distinctive tone placed on conductor 255 by the previously-described operation of the tone relay 414 informs the calling subscriber that no line is connected to the called terminals.

' Master-Switch opemzO-n For the purpose of completeness, further description will now be given of the opery It waspointed out hereinbetore how the master switch responds to an energization of thc start relay upon'the release of the connector,

,following a successful connection, resulting in an energization ol the locking magnetA 311 through the right-hand winding of the supervisory relay 317 to -disengage thelocking segment 303 and allow the assembly 'to' be driven in a counter-clockwise direction by vthe spring 304 until an idle trunk is encountered, at which time the start relay falls y back because relay 315 no ylonger encounters ground potential. The locking magnet 311 falls back at this time yand catches and holds the locking segment 303 so that the master switch remains in association with the idle trunk. When they selecting loperation has taken place until the master switch hasadvanced` to its limit in the counter-clockwisev direction, and the wipers 315 and 316 are on the contacts of trunk 1, the finger 309 of the ymaster switch presses the finger springs 302 into contact with each other, with the result that, in case the first trunkis `busy and relay 312 accordingly remains energized (or in case it is idle at the time and becomes y busy later), a circuit is closed through contacts of the start relay from the right-hand winding of supervisory relay 317, through the contacts 304, for the triprelay 305, whereupon relay 305 operates its springs 306 and 307 into engagement with the associated contacts, and the extension of spring 307 engages the latch 308 on f the springl controlledV by finger 310. Spring 307 closes 'an alternative circuit for the locking magnet 311, independent of the lower contacts of the start relay, so as to maintain the locking magnet energized and the locking segment freel for the time being, and spring 30,6 closes a circuit from the right-hand winding of supervisory relay 317 for the solenoid 301. Solenoid 301 draws in the associated plunger, rotating the .master-switch assembly in a clockwise direction to the position shown inthe drawing. Then this occurs, finger 310 engages the associated spring and moves it up, unlatching the spring 306 and allowing springs 306 and 307 to disengage their associated contacts.

This opens the circuit of solenoid 301, and it opensthe alternative circuit of the locking magnet 311, with the result that magnet 311 deenergizes, unless the start relay 312 .is energized in this yposition of the `master switch because of a busy condition .of the tenth trunk. In case the tenth trunk line is idle, or when an idle trunk line is reached in case the tenth trunk is busy, the locking magnet falls back and engages the segment and holds the master switchen the idle-trunk.

Supervisory apparatusv 4 .It is to be noted that the locking magnet 311 iis always energized while the master switch is operating, and that it always closes a circuit for the two windings of the supervisory relay 317 in series so that thesupervisory relay 317 is always energized during the operation of the master switch. As an extra precaution, the, ground potential for operating the various relays and magnets of the master switch, with 'the exception of start relay 312 is obtained through the low-resist'- ance right-hand winding of relay 317. The relay 317 closes a supervisory circuit through the master-'switch signaldamp 341 for the upper winding of relay 340. This relay is common to the master-switch signal circuits and the release signal circuits. Whenever this relay operates, either due to an operation of the master switch or to a releasing operation of the connector C of Fig. 2 (in the armature ofV Arelay 340 'engages is :a

weighted contact, and vit vibrates a 'few seconds after being struck bythe armature. Relay 339 adjusted so as not to operate while the weighted contact of the armature ofrelay 340 is vibrating. `Byfthis means, relay 339 does not operate,4 in the case cfav regular operation of the master switch or in the case .of a regular release of the connector, but only in case the connector is stuck and fails to release, or Athe master switch continues to operate `without findingan idle trunk. y l 1 When relay 339 operates,. after the vibrating contact of relay 340 has come to` rest with the armature inY an energized condition (which occurs only during an abnormal condition), it connects-the lower windingof relay 340 in parallel with'the upper high-resistance winding of the relay so as toenable the lamp 341 (or 342, as the'casemay be) to become lighted. At its upper armature, relay 339 closes a circuit for the buzzer 338 so as to notify an attendant repairman in caseV he is present. buzzer circuit is usually extended by meansof an auxiliary trunk circuit (not shown) over one of the trunk lines so that an"l alarm is sounded in the manual exchange.

Uurrent suppzg/ B through the fuses'331 and 332. The connection from the 'charging' source to [the grounded terminal ofbattery B is through the ground bus-bar 336 (instead of directly to the lower terminal ofthe battery) so as to operate the ammeter AAM either on charge or discharge. v :e The vvoltmeter VM is bridged across the' terminals 335 and336 to show the voltage of the batte-ry. In case a fuse associated withbus-bar 335 blows, ,one of the special spring'contacts, thereof' is forced into engagement A'with the bus-bar 337, closing a circuit from the battery bus-bar 335 over the bus-bar337 andthrough the associated lamp to the alarm relay 339.

Vhat is claimed is: 1. In a telephone system, a telephone line extending from a subscribers substation t0 a telephone exchange, a line relay connected to said line in the telephone exchange, a

It may be pointed out that the IUD source of current at the exchange, asou'rce of current at the substation, means at the substation for preparing a circuitover the telephone line forsaidlline relay, means for applying said source of current at the substation to the line to operate said relay, and

means responsive to an operation of said relay for closing the prepared holding circuit for the relay over the subscribers `line from the source of current at the exchange.'

' 2. In a telephone exchange system, a subscribers line extending from a subscribers substation to a telephone exchange. a line re-l lay for said line in the telephoneexchange, a source of current at the'exchange and a source of current at the substation. and means for operating'said relay from said' source of current at the substation and for closingr a locking circuit for the relay over the line from the source of current at Vthe telephone exchange. i f

3. In a telephone exchange system, a subscribers lineextending 'from a subscribers substation to a telephone exchange, a line relav for said line in the telephone exchange,A a source of current at the exchange and a source of current'at the substation` means for operating said relay from said source of current at the substation and for closing a locking circuit for the relay over the line from the source of current at the telephone exchange, a nonnumerical switching device. and means for operating said device responsive to the operation ofsaid line relay.

4. In an automatic telephone exchange system. a calling line, a called line, a current source on the calling line. a current source in the exchange. means Vin the exchange responsive to a current flow from the source on the calling line for setting up current flow over the line from the current source in the exchange. means on the calling line for. producing interruptions in the current flow from the source in the exchange` andan automatic switch in the exchange including a line relay directly responsive to said interruptions, said switch being responsive to said line relay to set upa connection between said lines.

V5. In an automatic telephone system, auto# matic switching `apparatus arranged to set up a connection from a calling line to a called line, a non-numerical switcli'arranged to ei'- fect aV connection from a calling'line to said automatic switching apparatus, a currentsource onthe calling line, a current-source in the exchange, circuit connections including aline relay in said non-numerical switch directly responsive to'current-ilow from the current-source onthe calling line foroperatingsaidnon-numerical switching apparatus, and means on the calling line for controlling the current-flow from the source at the exchange over the calling line for'operating said automatic switching apparatus.

6. Ina telephone exchange system,.a subscribers line entering the exchange, aline relaytor said line at the exchange', a current source at the exchange and va current source` on the line, circuit connections for operating 7. In a telephone system, a line entering ,a`

telephoneexchange, av current source in the exchange, a current .source on the line, a line relay in the exchange,l means for operating said line relay from the current source on the line and over the two conductors of the line inV series, and circuit connectionsformaintaining said line relay operated overa circuit path` from' the source in the exchange, over one conductor of said line and a return conductor separate from the other conductor of said line. f

8. YIn a party-line telephone system wherein lines terminate at the telephone exchange in individual lineswitches having access to a plurality of local trunk lines, an automatic switch common to said local trunk lines and having access to all of the said lines entering the exchange, means controlled over any calling one of said lines for operating the individual lineswitch to seize a local trunk line and for operating said automatic switch to effect a connection with a desired line, means individual to said automaticeswitch respon# sive to further control over the calling line for signalling the desiredfsubstation on a called party line, and means effective after the de-l siied subscriber on the party line has'been signalled 'for operating the lineswitch on the called line to connect with the same local trunk seized bythe lineswitch on the calling linev and for rele-asingsaid automatic switch.

9. In; an automatic telephone system, an automatic switch arranged to be controlled over a calling line to make connection with a called line, a; party selector associatedwith said automatic switch and arranged' to be set under the control of' the calling line in accordance with the desired station on the called line', atiming device associated with saidautomatic switch, means for operatingsaid timing device to free said automatic switch in case it is held for a predetermined time without being fully operated, and means including said timingdevice and eective when the said.

automatic switch and the associated party selector are fullyV operated to place ringing current on the called line inaccordance with the setting of said party selector.

'10. Ina telephone system, an automatic` switch arranged to; complete al connection from a calling line to a ldesired called line through one of its terminal sets, one terminal oi'-each set not connected to a line having ay specialconnection thereto, and means in said switch controlled over said special connection when the switch is set on a vacant terminal set for informing the calling party of the fact.

l1. In a telephone system, an automatic switch arranged to complete connections from a calling line to desired called lines through its terminal sets, one terminal of each set not connected to a line having a special connection thereto, and means in said switch controlled over said special connection for placing a distinctive tone on the calling line.

l2. In combination, an automatic switch having a line incoming thereto, aA line relay for said automatic switch having a line winding and a holding winding, said line winding being connected in circuit with said line, a current source, contacts `on said line relay closed responsive to an energization of said relay by current-flow through-said line and through the line windingI of the relay, additional contacts on said relay closed when the relay is additionally energize-d by currentflow from said current source through the holding winding, said additional contacts being arranged to short-circuit said line winding, an operating circuit for said automatic switch` and still other contacts on said line relay for controlling said operating circuit.

13. In combination, an automatic switch, a line incoming to said switch, a line relay for said switch having a line winding and a locking winding, contacts on said relay effective when current flows over the line and through the line winding to close a circuit for the relay through its locking` winding, operating contacts on said line relay for closing'an operating circuit for the automatic switch, contacts on the automatic switch for disconnecting the line relay from the line and for opening its locking circuit, and additional contacts on said line relay for short-circuiting the line winding thereof so as to render the relay slow to release and thereby enable it to maintain the operating circuit of the f' switch closed for an interval.

14. In combination, an automatic switch having a release magnet, ysupervisory apparatus, means for operating said automatic switch to establish a desired connection, means effective thereafter for closing a circuit for said release magnet and for closing a .y

circuit for said supervisory apparatus, said release magnet being responsive to the closure of its circuit to restore the switch to its normal position, off-normal contacts included in said release magnet circuit and opened responsive to saidswitch attaining its normal position, and additional olf-normal contacts included .in the circuit of said supervisory apparatus and opened responsive to said switch attaining its normal position.

l5. In an automatic telephone system, a connector switch arranged to extend connections to party lines, a party selector associated with said switch and having two wipers1 code signalling conductors dierently connected to the bank contacts of said two wipers, means effective after said connector has been set upon the terminals of a called party line and after said party selector has been positioned for .placing the signalling of the line under the controlof the first of said two wipers of the party selector, and means in said connector effective after the line has been signalled depending upon the setting of the first wiper for substituting the second wiper of the party selector for the first wiper.

16. In a telephone system, a connector switch having accessy to party lines, a code selector associated with said connector switch,

Vsaid code selector having two wipers, means for positioning said wipers in accordance with the code assigned to the desired party on a called party line, a ringing relay-and a reversing relay in said connector, a code signalling device and means for operating it to control said ringing relay through the first wiper of the code selector, and means for thereupon operating said reversing relay tol f shift the ringing relay under the control of the second wiper of the codel selector instead of the first.

In witness whereof, I hereunto subscribe my name this 23d dayof November, A. D.

NORMAN I-I. SAUNDERS. In witness whereof, I hereunto subscribe my name this 23d day of November, A. D. 1929. i Y

CLARENCE E. LOMAX. 

